A microphone is extensively used in a mobile device, an audio device, a vehicle, or the like to detect and convert a sound, that is, a sound wave, into a physical value or an electrical value. The converted signal is finally processed to a signal recognizable by a person or a machine.
Since the microphone receives a natural signal such as the sound wave, analog signal processing is essential to convert the signal. An analog signal processing circuit may have a direct influence on the entire performance of the microphone. Particularly, since the microphone receives a wide frequency range as an input due to a characteristic thereof, a noise characteristic is important.
Since a signal output from the microphone is a single signal, an output signal needs to be converted into a full differential signal that is advantageous for the noise characteristic. Further, an input stage DC bias function and an amplification rate control function to control a size, that is, sensitivity of the signal, may be essential in a fully differential structure. In general, the analog signal processing circuit is configured by a combination of circuits to implement the above functions. However, the combination of the circuits may result in an increase of electrical noise.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.